Titanium base alloy



United States meat 3,069,259 TITANIUM BASE ALLOY Harold Margolin, Mount Vernon, N.Y., Leonard S. Croan,

Alexandria, Va., William F. Kirk, New Haven, Conn., and Paul A. Farrar, Bronx, N.Y., assignors, by direct and mesne assignments, to the United States of America as represented by the Secretary of the Army No Drawing. Filed Nov. 10, 1959, Ser. No. 852,156

4 Claims. (Cl. 75-175.5)

This invention relates to high strength, tough, ductile titanium base alloys and is more particularly directed to a complex alloy system containing aluminum, vanadium, and tin as essential constituents.

3,069,259 Patented Dec. 18, 1962 ice tion in ductility and toughness heretofore encountered along with the increased strength. For example, as shown in Table II below, the addition of 0.50% Fe and 0.25% Cu to a Ti-5.5Al-5.5V-2Sn alloy heat treated as indicated vfor the Cl alloy increases the tensile strength up to a It has been found that a desirable combination of high above.

Table I 0.1 Y.S. 0.2% Y.S. Tensile Percent Percent Impact No. Alloy Heat treatment (p.s.i.) (p.s.i.) strength elongareduction ener y (p.s.i.) tion (1") in area -40 A1 Ti-6A1-4V 1,750 F.-1hr./WQ, plus 1,200 F.1hr./AC 1 139, 000 144,000 156,000 16. 4 45. 3 13. 5 A2 do 1,750 F.1hr./WQ, plus 1,100 F.1hr./AC 143, 500 147,500 159,500 14.1 44. 5 15.0 1,750 F.1hr./WQ, plus 900 F.1hr./AO 143, 000 149,000 164, 500 13. 0 32. 5 14.0 1,650 F.-2hr./'WQ, plus 1,000 F.1hr./AC 141, 500 147,000 162, 500 14. 1 41.0 12. 6 1,700 F.1hr./WQ, plus 1,150 F.-1hr./AC 152, 500 157,000 170,500 11.5 28.1 8. 8 1,650 F.'1hr./WQ, plus 1,150 F.1hr./AO 158,000 163,000 179,500 10.1 24.6 10. 1 1,600 F.-1hr./WQ, plus 1,100 F.1hr./AG.- 153, 500 158,000 171,500 10.4 27. 2 10.3 1,600 F.1hr./WQ, plus 1,050 F.1hr./AC 154,000 159, 000 178,000 9. 4 25. 4 10.0

v 1 WQ=Water quench. 9 AC =Air c001.

strength, toughness and ductility can be obtained by the As shown in Table II, slight increases in the amount of iron and copper together with a very small reduction proper heat treatment of a titanium base alloy having 6% aluminum and 4% vanadium. However, efforts to raise the tensile strength of this alloy above 165,000 p.s.i. by increasing the amount of the interstitial contaminants such as oxygen and nitrogen or by the addition of alpha or beta promoting elements have invariably resulted in an excessive reduction in the ductility, toughness, and impact strength of the resulting alloy. For example, as can be seen by reference to Table I above, while the addition of 2% each of vanadium and tin to the basic Ti-6Al-4V alloy increases the tensile strength by as much as 20,000 p.s.i. or 12 /2% when alloys A2 and B2 are compared, the elongation in one inch drops almost 30%, the reduction in area falls about 45% and the impact energy at in the amount of aluminum serve to improve the mechanical properties while slightly reducing the maximum attainable tensile strength. Such improvement is particularly noticeable in regard to the ability of the alloys to absorb impact energy at -40 F. which reaches a maximum of 13.4 ft.-lbs. even though the tensile strength is at the very high value of 197,000 p.s.i.

As shown in Table I, V-notch Charpy impact values at 40 F. of between 12.5-15.0 have heretofore been attained only where the tensile strength values were below 164,500 p.s.i. While tensile strengths of over 165,- 000 p.s.i. can be attained in some titanium base alloys, such accomplishment is generally accompanied by a sub- F. is reduced by about 33 /s%. stantial decrease in ductility as shown by the elongation Table II V-notch 0.1% 0.2% Tensile Percent Percent Charpy No. Alloy Heat treatment Y.S. Y.S. strength elongareduction impact (p.s.i.) (p.s.i.) (p.s.i.) tion in in area at 40 1" F. (ft.-

lbs.)

C1 'Ii-5.5Al-5.5V-2Sn-0.5Fe-0.25GU-- 1,7h25f6 1hr./WQ, p1us1,100F.1 194,000 200,500 208,000 8.0 30.1 9.0

1. C2 Ti-5.5Al-5.5V-2Sn-0.5Fe-0.25CU. 1,(15;75A12 hr./WQ, plus 1,000 F.1 192,500 200,000 208,000 9.4 39.0 8.3

I. C3 Ti-5.5A1-5.5V-2Sn-0.5Fe-0.25Cu..- l,%i5AF-2 hr./WQ, plus 1,100 F. 181,300 186,000 194, 000 11.0 46.6 7.6

1. G4 Ti-5.5A1-5.5V-2Sn-0.5Fe-0.250n 1,6]25336-2 hrJWQ, plus 1,000 F. 190,000 193,000 198,500 13.2 54.7 8.8

I. D1 Ti-5.25Al-5.5V-2Sn-0.9Fe-0.25Cu 1,612316-3 hr./WQ, plus 150 F.-1 176,000 179,000 188,000 10.3 43.6 12.1

I. E1 Ti-5.25A1-5.5V-2SI1-0.9Fe-0.5Cu. l,5h87AF-3 hr./W Q, plus 1,050 F.1 181,000 182, 500 188,300 10.0 33. 5 13.0

T. F1 Ti-5.25Al-5.5V.2SI10.9Fe-1.00u... 1,51612 FA(J3%hr./WQ, plus 1,050 F. 191,000 193,000 197,000 9.2 36.3 13.4

I. G1 Ti-5.25Al-5.5V-2Sn-1.15Fe-0.250u.- 1,5h877f63 hr./WQ, plus 1,050 F.l 178,000 180,000 189,500 9.3 25.8 11.5

1 WQ=Water quench. 1 AG=Air cool.

The present invention is based upon the discovery that the addition of relatively small amounts of iron and copper to the basic Ti-6Al-4V alloy along with 2% Sn and an additional 2% V will provide a substantial increase in tensile strength without the customary large reducvalues in U.S. Patent No. 2,739,887, dated March 27, 1956. Although U.S. Patent 2,884,323 dated April 28, 1959, which teaches the attainment of very high tensile strengths through the inclusion of over 0.4% oxygen, does not show the expected drop in the values for the elongation and reduction in area, this unusual result does not extend to the ability of the alloy to absorb impact energy which is reduced to 5.5 ft.-lbs. The toughness of titanium base alloys is highly important in ordnance applications wherein unusually high impact forces are freqnently encountered.

The, compositions of the alloys listed in Tables I and II are nominal percentages measured in terms, of weight indicative ofthe exact analyzfid values and. are utilizedfor he sake f r i i' v The sum of the interstitial elements in the alloys of TableII is maintained below 0.25% withoxygen below 0.2%, nitrogen below 0.05% and carbon below 0.1%..

The alloys. of'Table II were cast as 3%" diameter ingots weighing approximately 6" lbs. Initial forging was accomplished at a temperature up to 300 F. in excess of the temperature at, which a 100% beta structure is stable, commonly referred to as the beta transus. These ingots were forgedto a 2" square bar, reheated to 150 F. above the beta transus and thereafter forged to a 1" square. 50 F.-75 F. below the beta transus temperature andrthen forged to; V2 square. These barswere heattreated as indieated'in Table II and were, then machinedto. provide the necessary tensile and'Charpy impact specimen.

Accordingly, the complex alloys of the present invention. can bevheat treated to provide. tensile strengthsin thevicinity. of 200,000 p.s.i. while maintaining goodielon gation, reduction inarea, and impact strengthvalues. At lower tensile: strengths which, howevenare still above the maximum which can be attained witli-thezwell-known Ti-6Al-4V alloy, the ductility values can; even be appreciably enhanced by varying the composition of the alloy and the heat treatmentthereof to a slight extent.

Althougha particular embodiment of the invention has been described indetail herein, it isevident that many variations may be. devised'with'in the spirit and scope thereof and. the following claims are intended to: include such variations,

We claim:

1. A titaniumbase mixed'phase alpha-beta allfoy consisting of, by weight, from.5%6% Al, %.-6I% V, 2% Sn, 0.201.5%. Fe and 0.1,0-1.5'%1 Cu andlthe balance titanium with incidental impurities.

The resulting bar was then reheated to between:

4 US. Ofiice of Technical Services Report PB 131502, November 1956, 100 pages.

2. A titanium base mixed phase alpha-beta alloy consisting of, by weight, from about 5%-6% Al, 5%6% V, 2% Sn, 0.20-1.5Fe and 0.l0l.5% Cu and the balance titanium with the sum of oxygen, nitrogen, and carbon below 0.25%, and characterized by a tensile strength in excess of' 185,000 p.s.i. with good. ductility and toughness.

3.. A titanium basemixed phase alpha-beta alloy consisting of, by weight, from about 5%-6.% Al, 5%6% V, 2% Sn, 0.201.5% Fe, and 0.10-1.5% Cu and the balance titanium with incidental impurities, said alloy having a tensile strength ranging up to 208,000 p.s.i with good ductility and excellent impact energy at 40 F. when solution treated at a temperature of about F F. below the beta transus temperature. followed by a water quench and thereafter aged at a temperature of about 1000 F.1100 F;

4; A titanium base mixed phase alpha-beta alloy consisting of, by weight, from about 5.25% Al, 5.5% V, 2% Sn, 0.9% Fe. and 1.0%. Cu and the. balance titanium with incidental impurities and interstitials below 0.25 characterized by a tensile strength of 197,000 p.s.i., an elongation in one inch of 9.2%, a reduction in area of 36.3% and a V-notch Charpy impact energy values at 40 F.

of. 13.4 ft.-lbs;, when heated to. l5i62 F. for 3 /2 hours and" water quenched followed by agingfor 1 hour at1050 F. and air cooked therefrom.

References Cited' inthefile'of this patent UNITED 1 STATES PATENTS 2,754,204 Jaffee et a1. July 10, 1956 2,892,705" Jatfee et al. June 30, 1959' 2,893',864 Harriset'al July 7, 1959' 2,918,367 Crossley'et al. Dec. 22, 1959 OTHER REFERENCES Kirk et. al.: Development of Tough, High-Strength Quaternary Titanium-Base. Alloys of the Ti-Al-V-X System, New York University (Watertown Arsenal Labs),

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,069 ,259 December 18, 1962 Harold Margolin et a1.

It is hereby certified that error appears in the above numbered pat ent requiring correction and that the said Letters Patent should read as corrected below.

Columns 1 and 2, Table 11, under the heading "Heat Treatment" and opposite alloy No. "D1", for "150 F." read 1,050 F. column 4, lines 1 and 2, strike out U,S.. Offi of Technical Services Report PB 131502, November 1956, 100 pages."; line 29, for "cooked" read cooled line 42, after "(Water-town Arsenal Labs.) insert Uc.S. Office of Technical Services Report PB 131502, November 1956, 100

pages.

. Signed and sealed this 22nd day of October 1963.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer AC ing Commissioner of Paten' 

1. A TITANIUM BASE MIXED PHASE ALPHA-BETA ALLOY CONSISTING OF, BY WEIGHT, FROM 5%-6% AI, 5%-6% V, 2% SN, 0.20-1.5% FE AND 0.10-1.5% CU AND THE BALANCE TITANIUM WITH INCIDENTAL IMPURITIES. 